Scalar Quadratic-Gaussian Soft Watermarking Games

TL;DR

This paper models soft watermarking as a zero-sum game involving a continuum of embedded information, deriving optimal strategies for linear encoders and Gaussian-affine attackers, with numerical insights into system behavior.

Contribution

It introduces a novel game-theoretic framework for soft watermarking with a continuum of information and derives optimal strategies for linear encoders and Gaussian-affine attackers.

Findings

Optimal attacker is Gaussian-affine for linear encoders.

Derived system parameters for optimal watermarking.

Numerical results illustrate system behavior at equilibrium.

Abstract

We introduce the zero-sum game problem of soft watermarking: The hidden information (watermark) comes from a continuum and has a perceptual value; the receiver generates an estimate of the embedded watermark to minimize the expected estimation error (unlike the conventional watermarking schemes where both the hidden information and the receiver output are from a discrete finite set). Applications include embedding a multimedia content into another. We consider in this paper the scalar Gaussian case and use expected mean-squared distortion. We formulate the resulting problem as a zero-sum game between the encoder & receiver pair and the attacker. We show that for the lin- ear encoder, the optimal attacker is Gaussian-affine, derive the optimal system parameters in that case, and discuss the corresponding system behavior. We also provide numerical results to gain further insight and understanding of the system behavior at optimality.